Lithium transport in a macrocyclic electrolyte - art. no. 214201

We have carried out nuclear magnetic resonance (NMR) studies on a new class of electrolyte consisting of a lithium salt (LiMPSA) and a macrocycle ([2. 2.2] cryptand). NMR diffusion coefficient measurements have determined the motion of lithium cations (Li-7-NMR), polyatomic anions (MPSA) (F-19-NMR), and encapsulating macrocycles ( H-1-NMR), with the striking result that the y are equal over a large temperature range. Diffusion coefficients as low a s (1.0+/-0.1) 10(-9) cm(2)/s have been measured through the use of a 42 T/m fringe-field gradient. The magnitudes of the anion and cryptand diffusion were found to be consistent with a free-volume picture for translational di ffusion. The transport of the lithium cations was interpreted as taking pla ce mainly through association with large anions (MPSA) and encapsulating ma crocycles ([2.2.2] cryptand), with averaged residence time fractions of 77 and 23 %. respectively. NMR spin-lattice relaxation time measurements of Li -7 and F-19 spins have also been performed.